The present invention is generally directed to a polymerization processes for the preparation of narrow polydispersity homopolymers and copolymers and which polymerization processes are facilitated and mediated by stable free radical agents. More specifically, the present invention relates to improved reliabilities, enhanced rates, and reduced costs in stable free radical mediated polymerization processes for obtaining homopolymers and copolymers, such as block, multiblock, graded or tapered, and branching copolymers containing a variety of known free radical polymerizable monomers and which polymers and copolymers have narrow molecular weight distribution properties and are obtained in high conversions. Even more specifically, the present invention relates to improved free radical polymerization processes that use, in embodiments, and least one free radical polymerizable monomer, and in embodiments, for 1 to about 10 different monomers, a conventional free radical initiator compound, a stable free radical compound, and a reducing agent, for example, a reducing sugar such as glucose, and the like compounds, to obtain the aforementioned polymer and copolymer products. In embodiments of the present invention, the polymerization process can be accomplished wherein the free radical initiator compound and the stable free radical compound are separate entities, or alternatively, combined into a single molecular entity or an initiator adduct, such as a "unimer" or an oligomer, that is, a compound containing both a "masked" free radical initiator species and a covalently bonded and thermally labile, in a reversibly dissociable sense, stable free radical moiety. Thermal decomposition of the initiator adduct, as in the "unimer" or the oligomer, liberates the free radical initiator component and the stable free radical component into the polymerization reaction mixture. From detailed kinetic and mechanistic studies of stable free radical mediated polymerization processes it is known that excess amounts of the stable free radical agent, while useful in substantially controlling thermal polymerization and polydispersity broadening processes, can provide a source of substantial inhibition, or at least retardation of the rate of monomer polymerization. Thus, in embodiments, it is desirable to maintain a balanced or low steady state concentration of the "free" or liberated stable free radical agent and at a level which is capable of substantially inhibiting undesirable pathways, such as premature and irreversible polymer chain termination, disproportionation, interchain coupling, and the like processes, while leaving unimpeded productive polymerization pathways. The reducing agent is believed to accomplish the desired balanced condition by chemically reducing excess amounts of stable free radical compound and thereby enabling acceleration of the overall rate of stable free radical mediated polymerization processes.
The present invention relates to processes for the preparation of polymers, and more specifically to stable free radical mediated free radical polymerizations and copolymerizations, and to polymeric resins formed thereby. In embodiments, the present invention relates to a stable free radical moderated polymerization and copolymerization process for producing a thermoplastic polymer resin or resins, that have narrow polydispersities, that is, narrow molecular weight distributions as defined by the ratio Mw:Mn, where Mw is weight average molecular weight of the polymer and Mn is number average molecular weight of the polymer, with an easily controllable modality, from at least one free radical polymerizable monomer compound comprising:
heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent additive, wherein there results a thermoplastic resin or thermoplastic resins with a narrow polydispersity, for example, of from about 1.1 to about 2.2 and in high conversions, for example, of from about 50 to 100 percent; PA1 cooling the mixture to effectively terminate the polymerization; optionally isolating the thermoplastic resin product; and optionally washing and drying the polymer resin products. PA1 overcoming, or minimizing deficiencies of prior art processes, by providing processes with improved efficiency, improved flexibility, and improved operational economies; PA1 providing a process for the preparation of a resin comprising: heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent. PA1 providing a process for the preparation of a resin, especially a thermoplastic resin, or thermoplastic resins comprising: heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent additive, wherein there results a thermoplastic resin or thermoplastic resins with a narrow polydispersity of from about 1.1 to about 2.2, preferably from about 1.1 to about 1.5 and in high conversion of from about 50 to 100, and preferably from about 70 to about 90 percent; PA1 providing a process for the preparation of a thermoplastic resin, or thermoplastic resins comprising: heating a mixture of at least one free radical polymerizable monomer, a thermally labile unimer or oligomer initiator compound comprising a free radical initiator component and a stable free radical component, and a reducing agent additive, wherein there results a thermoplastic resin or thermoplastic resins; and PA1 providing stable free radical mediated polymerization processes for the preparation of block and multiblock copolymer thermoplastic resins comprising: heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent additive, to form a first intermediate product resin; and thereafter repeatedly reacting the resulting product with successively added monomers which monomers are different from the previously polymerized monomer to form well defined block and multiblock copolymer thermoplastics. PA1 heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent. PA1 heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound, and a reducing agent additive, wherein there results a thermoplastic resin or thermoplastic resins with a narrow polydispersity of from about 1.1 to about 2.2 and in high conversion of from about 50 to 100 percent. PA1 heating a mixture of at least one free radical polymerizable monomer, a free radical initiator compound containing or integrating a covalently bonded stable free radical agent, and a reducing agent additive, wherein there results a thermoplastic resin or thermoplastic resins with a narrow polydispersity of from about 1.1 to about 2.0 and in high conversion of from about 50 to 100 percent. In embodiments, the free radical initiator compound can be of the formula R'--SFR, wherein R' is an oligomeric compound comprised of from about 1 to about 30 monomer units and optionally a covalently bonded free radical initiator compound, and wherein --SFR is a covalently bound stable free radical group. In embodiments, the free radical initiator adduct compound R'--SFR can be, for example, N-(1-methylbenzyl)-oxy-2,2,6,6-tetramethyl-1-piperidine (MB-TMP ) of the formula ##STR2## PA1 heating a mixture of alkyl acrylate free radical polymerizable monomer and non-acrylate free radical polymerizable monomer, a free radical initiator compound containing an integral and covalently bonded stable free radical compound, for example, of the formula ##STR4## and a reducing agent additive such as glucose, an optionally a basic compound, wherein there results a thermoplastic resin copolymer of the alkyl acrylate and non acrylate monomers with a narrow polydispersity of from about 1.1 to about 2.2 and in high conversion of from about 50 to 100 percent. PA1 heating a mixture of a free radical polymerizable monomer, a free radical initiator compound, a stable free radical compound which separate and apart from the free radical initiator compound or is integral therewith, and a reducing agent, to form a mixture containing a first intermediate product resin, PA1 optionally cooling the resulting mixture; PA1 optionally isolating said first intermediate product resin from the mixture; PA1 adding to said first intermediate product resin a second mixture comprised of at least one free radical polymerizable monomer compound, and optionally a reducing agent, wherein said polymerizable monomer compound of said second mixture is different from said polymerizable monomer or monomers of said first mixture, to form a combined second mixture; PA1 heating said combined second mixture to form a third mixture comprised of a block copolymer thermoplastic resin comprised of a first product resin formed from said first intermediate product resin and added said second monomer; PA1 cooling the resulting third mixture; PA1 optionally isolating the resin from said third mixture; PA1 sequentially repeating the preceding three steps of adding, heating and cooling, N times, wherein N represents a number, to form a fourth mixture containing a multiblock copolymer thermoplastic resin or resins having N+2 blocks and wherein N is the number of times said sequence is repeated; PA1 optionally isolating said multiblock copolymer thermoplastic resin from said fourth mixture; and PA1 optionally washing and drying said multiblock copolymer thermoplastic resin and wherein said multiblock copolymer thermoplastic resin possesses a narrow polydispersity and a modality of 1.
In another embodiment polymeric chain growth proceeds by a pseudoliving mechanism and can provide resins of variable molecular weights (Mw) from very low to very high, for example, less than about 10,000 up to about 200,000, and more specifically from about 8,000 to about 200,000, while maintaining narrow molecular weight distributions or polydispersities. In another embodiment block and multiblock copolymers can be synthesized by the aforementioned stable free radical moderated polymerization processes wherein each block formed is well defined in length by the added and reacted monomer and wherein each additional block that is formed also possesses a narrow molecular weight distribution.
The present invention is directed to polymerization processes which permit the economic preparation of narrow polydispersity resins with low, intermediate, or high molecular weights. The low molecular weight resins can be prepared without a chain transfer agent or molecular weight modifier which provides several advantages over conventional polymerization processes as illustrated herein.
The stable free radical mediated polymerization system of the present invention s can readily afford narrow polydispersities, in embodiments, of from about 1.05 to about 2.0 for homopolymers, and in embodiments, of from about 1.1 to about 1.6, and as low as 1.5 or below for various copolymer systems. Stable free radical mediated polymerization systems of the present invention afford resin polydispersities that are comparable to those obtained in anionic polymerizations.